1. Field of the Invention
The present invention relates to the treatment of molten glass contacting surfaces employed in manufacturing glass articles, and more particularly to a process of treating such surfaces with an organic solution of metal organic phosphate having dispersed therein a finely-divided lubricious filler, the suspension being adapted to forming a degradation product on such surfaces on heating to enhance the rapid release of the newly-formed glass articles from molding and handling surfaces, and to protect such surfaces from excessive wear.
2. Description of the Prior Art
In conventional glass forming processes employed in the molding of glass containers, such as bottles, jars, and the like, the mold surfaces are frequently treated with a release coating by a technique known as swabbing. Normally, swabbing of glass molds is carried out by the utilization of a mop-like brush and a swabbing composition or compound which is placed upon the surface of the glass molds by brushing the mold forming surfaces with the compound. In many cases, the swabbing compound is composed of a mineral oil base with a lubricant, such as powdered graphite, and in some cases a wetting agent. Such material is brushed or "swabbed" upon the glass molds on the surfaces at which the glass comes in contact with the mold and this is accomplished every 5 to 30 minutes. The swabbing composition, placed onto the mold, is used to form a quick release surface for the glass which is being formed and utilization of this material decreases the chances of blemishes or defects on the glass container surfaces and protects the mold itself. Some compounds utilized in making swabbing materials include graphite, oil, sulfur and cork. These materials, when subject to the heat provided by the molten glass, produce corrosive materials, specifically sulfuric acid, which attacks the exposed metals of the mold and other glass forming equipment. Furthermore, because of the manual swabbing techniques, where the material is applied by the operator to the glass molds, uneven coatings or swabbing may be harmful. As a result, over a period of time, there is a build-up of mold swabbing composition residue, from burn-off within the mold, and this build-up can cause the formation of a defective and undesirable glass container. The oil swabbing materials frequently result in molded glass containers which are discolored or blemished and must be rejected.
Additionally, the use of oily swabbing compounds result in a great deal of smoke and airborne residue due to the heat at which the glass molds and equipment are operated in order to produce and form the glass containers. As a result, conventional swabbing techniques, with oil, create significant problems to the environment with respect to air pollution.
The utilization of solid film lubricants or quick release agents on the surface of the glass molds is useful in that such practice employs a coating for the glass molds and at the same time provides a quick release of the newly-formed article. This virtually forms a complete protective coating for the mold surface and avoids the disadantages of the swabbing technique which were previously stated.
However, in many cases, for example U.S. Pat. Nos. 4,003,867, 3,977,885, 3,783,013, and 3,994,847, various types of metal-phosphate binder solution are disclosed which are aqueous and strongly acidic. The main objection to these particular binding solutions which form a coating upon the mold is that while they are difficult to apply, more to the point, they are extremely corrosive to the substrate, usually a metal such as steel. Aqueous solutions when applied normally require a spray application to a hot metallic substrate so that the water is flashed off rapidly and the binder converted to a neutral salt thereby minimizing corrosive reactions. In order to accomplish the necessary treatment for glass container molds, a number of very thin coatings is required, each being allowed to dry before the next coating application is carried out. Obviously, these methods are not readily adaptable to production where rapid, foolproof applications are preferred and a known thickness of resultant coating is required. This invention provides a process for treating the molds and other glass handling equipment used in the manufacturing of glass containers and other glass articles which avoids the disadvantages of the prior art with respect to aqueous solutions.